This is a sliding vane pump or engine similar to the Ramelli pump model in F-4 illustrated in his 16th century book of machine engravings. In the Beale model however the sliding vane is split. As the excentric cylinder is turned by a crank in the rear, the two halves of the vane slide so as to seal or move along the inside surface of the fixed cylinder or chamber. The sliding vanes are cleverly actuated by connecting the outer corners of the vanes to sliding joints along the back edge of the cylinder. As a pump, the rotating cylinder moves fluid-water or air from the entrance to the exit in one of the moving volumes of the split chamber. Reuleaux called mechanisms of the F series type, chamber-crank kinematic trains.

As an engine, steam, compressed air or combusting gases in one of the two chamber spaces create pressure on one side of the sliding vanes thereby producing a force moment to turn the inner cylinder.